I am having difficulty with overall consistent results in the marbling process. In my recent attempts I have been using Jacquard marbling inks on a room temperature carrageenan size prepared 24 hours prior. My class has had some very successful results where paints float and spread beautifully. Other days they just sink to the bottom with horrible results and frustrated students. I have tried everything; thinning with water, dispersant, ox gall, photo flo yet nothing will get them to float. I am wondering is it the tap water? Any advice greatly appreciated!